Don't use PassRefPtr arguments for Range constructors/factories.

This usage of PassRefPtr was wrong because it didn't move ownership of
objects. We should use raw pointers and increase reference counters when it is
necessary.

BUG=none
TEST=none; no behavior changes.

Review URL: https://chromiumcodereview.appspot.com/23506015

git-svn-id: svn://svn.chromium.org/blink/trunk@157067 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Assume FrameView::m_frame is never NULL

FrameView::clearFrame() is unused and we never pass a null frame pointer to FrameView::create(),
so FrameView::m_frame should never be NULL. This removes FrameView::clearFrame() and
removes m_frame check from conditional expressions.

BUG=
R=abarth@chromium.org

Review URL: https://codereview.chromium.org/23483024

git-svn-id: svn://svn.chromium.org/blink/trunk@157068 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make CSSRuleList.item() index argument mandatory

Make CSSRuleList.item() index argument mandatory to match the specification:
http://www.w3.org/TR/DOM-Level-2-Style/css.html#CSS-CSSRuleList

This behavior is consistent with Firefox 23 and IE10. It is confusing what
should be returned if the index is omitted.

BUG=
R=arv@chromium.org, tkent@chromium.org

Review URL: https://codereview.chromium.org/23682005

git-svn-id: svn://svn.chromium.org/blink/trunk@157069 bbb929c8-8fbe-4397-9dbb-9b2b20218538